Convertible series/parallel regenerative blower

ABSTRACT

A regenerative centrifugal blower includes first and second toroidal working chambers formed in first and second abutting housings and separated by an impeller having blades extending from opposite sides into the working chambers. Each housing includes a port communicating with the working chamber and extending through the housing and a transfer duct adapted to align with the transfer duct or port of the other housing. The ducts and ports are positioned around the periphery of the housings in selected alignment such that when the housing members are secured in a first position, the working chambers are coupled in parallel and when the housings are relatively rotated approximately 45*, the working chambers are coupled in series. Thus, a single blower is convertible for either a relatively high pressure and low flow rate output or relatively high flow rate at a reduced output pressure.

United States Patent 11 1 Vander Linden Oct. 28, 1975 CONVERTIBLE SERIES/PARALLEL REGENERATIVE BLOWER [75] Inventor: lDale B. Vandel' Linden, Dowagiac,

Mich.

[22] Filed: Mar. 29, 1974 [21] Appl. No.: 456,008

[52] US. Cl. 415/153 A; 415/213 T; 415/199 T 51 Int. (:1. F041) 13/00 [58] Field of Search 415/53 T, 199 T, 153 A, 415/213 T [56] References Cited UNITED STATES PATENTS 1,973,669 9/1934 Spoor 415/53 T 1,979,621 11/1934 Hollander 415/199 T 2,045,851 6/1936 Hamilton 415/213 T 2,321,934 6/1943 Pato 415/213 T 2,768,808 10/1956 Worre 1 415/80 3,135,215 6 1964 Smith 415/199 T 3,761,203 9/1973 Neidhardt 415/213 T FOREIGN PATENTS OR APPLICATIONS 143,920 10/1951 Australia 415/53 T 777,161 11/1934 France ..4l5/213T Primary Examiner-Henry F. Raduazo Attorney, Agent, or Firm-Price, Heneveld, Huizenga & Cooper [5 7 ABSTRACT A regenerative centrifugal blower includes first and second toroidal working chambers formed in first and second abutting housings and separated by an impeller having blades extending from opposite sides into the working chambers. Each housing includes a port communicating with the working chamber and extending through the housing and a transfer duct adapted to align with the transfer duct or port of the other housing. The ducts and ports are positioned around the periphery of the housings in selected alignment such that when the housing members are secured in a first position, the working chambers are coupled in parallel and when the housings are relatively rotated approximately 45, the working chambers are coupled in series. Thus, a single blower is convertible for either a relatively high pressure and low flow rate output or relatively high flow rate at a reduced output pressure.

17 Claims, 17 Drawing Figures U.S. Patent' Oct. 23, 1975 SheetlofS 3,915,589

so 25 I IO o g o 27 22 24 c as 45 o as 26 0 as u FIGJ 11 U.S. Patent Oct-28,1975 Sheet30f5 3,915,589

US. Patent Oct. 28, 1975 Sheet4 0f5 3,915,589

FIG. H

CONVERTIBLE SERIES/PARALLEL REGENERATIVEBLOWER BACKGROUND OF TI-IE INVENTION This invention relates to regenerative type gaseous blowers'and particularly, to such a blower convertible for series or parallel operation of a pair of working chambers therein.

Regenerative ty'pe centrifugal blowers with either a single or two working chambers are known and possess significant advantages over positive displacement type compressors, centrifugal blowers or other conventional blowers. With regenerative blowers, the pressure achievable is significantly increased by a unit which is considerably more compact and includes fewer moving parts subject to wear than other conventional air moving devices/Also, regenerative type blowers typically can operate at slower speeds, reducing the noise of operation and wear of the unit. The improved results achievable with such blowers are attributed to the regenerative compression of air by the blades of the impeller causing the air to circulate in a spiral pattern as it flows along the toroidal path of the working chamber.

In some applications, a relatively high 'flow rate at a low pressure is required while in others, a higher pressure and low flow rate is necessary. To accommodate these competing requirements, the prior art suggests employing two separate regenerative blowers having their outputs coupled either in series to form a twostage blower with relatively high output pressure but at a low flow rate or coupled in parallel to increase the flow rate. at a reduced pressure.

Additionally, US. Pat. No. 3,694,101 issued Sept. 26, 1972 to R. D. Rumsey suggests a centrifugal regenerative blower having a single impeller communicating with a pair of working channels in a single unit. The unit disclosed can be adapted for either parallel operation of the separate working channels or, with significant modifications including the use of additional parts, series operation of the two working channels. Also, US. Pat. No. 3,545,890 issued Dec. 8, 1970 to A. B. Hubbard et al. suggests a regenerative blower with two separate impellers associated with a pair of separate working channels permanently coupled for series operation.

SUMMARY OF THE INVENTION The system of the present invention, however, represents a significant improvement over the relatively complex structure disclosed in the prior art and one in which substantially identical housings, rotatable with respect to one another, are abutted for series or parallel operationof the blower without requiring additional parts or interconnections. The resultant structure is a relatively uncomplicated blower including a unique impeller with aperipheral flange separating the working chambers formedin the housings. By providing such structure, the cost of manufacturingand maintenance of the blower is significantly reduced and it is easily convertible to provide series or parallel operation to satisfy the different requirements of individual applications. The simplicityof structure also significantly reduces the probability as reduceswear:

Apparatusembodying the present invention includes first and second circular housings, each including an" of failure of components as well along one side. Each housing includes a port extending through the housing wall and a transfer duct spaced from said port and including means for transferring air from the working chamber into or out of the duct or port. The housing members are secured to each other with a generally disc-shaped impeller therebetween which includes a peripheral flange sealing the working chambers from one another. The housings are rotatable with respect to one another for parallel or series connection of the working chambers.

It is an object, therefore, of the present invention to provide an improved regenerative blower having housing members rotatable with respect to each other for coupling a pair of working chambers in either series or parallel.

A further object of the present invention is to provide an improved regenerative blower of simplified construction and reduced cost.

Still a further object of the present invention is to provide an improved impeller for a regenerative blower with a peripheral flange for sealing a working chamber in a first housing from a working chamber in a second adjacent housing.

These and other objects of the present invention will become apparent upon reading the following description thereof together with the accompanying drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front elevational view of the blower; I

FIG. 2 is a top plan view of the blower shown in FIG. 1 with the front and rear housings coupled for parallel operation;

FIG. 3 is a rear elevational view of the blower shown in FIGS. 1 and 2 with the drive motor removed;

FIG. 4 is an enlarged cross section of the blower with the motor removed except for its drive shaft and taken along section lines lV-IV of FIG. 1;

FIG. 5 is a front elevational view of the inside of the front housing member of the blower;

FIG. 6 is a front elevational view of the inside of the rear housing of the blower;

FIG. 7 is a reduced front elevational view, partly in schematic form, of the impeller shown in FIG. 4;

FIG. 8 is an enlarged, fragmentary cross-sectional view of a segment of the impeller shown in FIG. 7 and taken along the section lines VIII-VIII of FIG. 7;

FIG. 9 is an enlarged, fragmentary cross-sectional view of a segment of the front housing taken along the section lines IX-IX of FIG. 5;

FIG. 10 is an enlarged, fragmentary plan view of the outlet port of the front housing taken in the direction of arrow 10 in FIG. 5;

FIG. 11 is an enlarged, fragmentary cross-sectional view of a portion of the rear housing taken along the section lines XI-Xl of FIG. 3-,

FIG. 12 is an enlarged, fragmentary cross-sectional view of the blower taken along the section lines XII- XII in FIG. 2;

FIG. 13 is an enlarged, fragmentary cross-sectional view of a segment of the blower taken along section I lines XIIIXIIl of FIG. 2;

annular working-chamber formed therein and open portion of the blower shown in FIG. 14 taken along the section lines XV-XV of FIG. 14;

FIG. 16 is an enlarged, fragmentary cross-sectional view of a portion of the blower taken along the section lines XVIXVI of FIG. 14; and

FIG. 17 is an enlarged, fragmentary cross-sectional view of a portion of the blower taken along the section lines XVIIXVII of FIG. 14.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Initially, it is noted that although the blower is described in terms of providing an output flow of air, it is to be noted that in addition to pressure application, the blower can be coupled with the inlet to a device for suction applications as well. Thus, although the terms inlet port and outlet port are used in the description of the blower, it is to be understood that the blower can be coupled to the utilization device for either pressure or suction purposes. Also, although the blower is typically used for supplying air flow, it is understood that the blower can be utilized for providing a flow of any gaseous or significantly compressible fluid.

The blower assembly of the present invention basically comprises front and rear housing members which are rotatable with respect to one another and secured to each other for series or parallel operation. A motor is mounted to the rear housing and includes a shaft extending into the housings for attachment of an impeller fitted between the two housings forming halves of the blower to seal an annular working chamber in the front housing from the annular working chamber in the rear housing. The rear housing includes an air inlet port communicating with the working chamber and a transfer duct spaced from the inlet port and separated by means for directing air flow from the working chamber into the transfer duct. The front housing, which is substantially identical, includes the same elements. Having briefly described the blower assembly, a detailed description of the construction of the housings, the impeller and their interconnection follows.

Referring now to FIGS. l-7, the blower includes a drive motor 12 and front and rear housings 20 and 50, respectively, surrounding an impeller 60 (FIGS. 4 and 7). Housings 20 and 50, as can be seen by comparing FIG. 1 with FIG. 3 and FIG. 5 with FIG. 6, are identical castings made, in the preferred embodiment, from aluminum. The only notable difference between the front and rear housings is the final machining necessary for -the mounting of the motor to the rear housing as described below. Since the housings are essentially identical, only a detailed description of the front housing is presented and identical parts of the rear housing will be identified by the same reference numeral preceded by the digit 1.

The exterior of housing 20 includes a central hub 22 (FIGS. 1 and 4) surrounded by an annular recessed area 23 in turn surrounded by an upstanding annular shoulder 24. Shoulder 24 of housing 20 includes motor mounts 24' (FIGS. 2 and 14) secured thereto at spaced intervals around the annular surface 24 to permit mounting of the blower with the drive shaft vertically oriented and the exterior of housing 20 facing the mounting surface. Mounts 24 can be conventional shock type motor mounts, as shown, or simply bolts. Shoulder 124 of rear housing 50 serves as a mounting boss for the electric drive motor 12. A plurality of cooling fins 25 extend radially outwardly from the face of the housing between shoulder 24 to the outer surface 26 of a working chamber 36 (FIGS. 4 and 5). Fins 25 span narrowed portion 25 between shoulder 24 and outer surface 26 of working chamber 36. Working chambers 36, 136 are substantially rectangular in cross section with rounded corners and the housings are cast with the working chambers opening along one side of the inside of the housings. The working chambers extend around approximately 315 of the housings as best seen in FIGS. 5 and 6. Extending from the outer surface 26 of the working chamber to a peripheral flange 28 extending around the entire housing is a plurality of radially extending outer fins 27.

Flange 28 includes a plurality of apertures 29 for receiving bolts 11 which sealably secure the front and rear housings in either the parallel connection, shown in FIG. 2, or in series connection as seen in FIG. 14. The front housing 20 includes an outlet port 30 which, as best seen in FIGS. 1, 5, 10 and 14, comprises an enlarged port housing 30 formed in the casting and having substantially flat outer peripheral surface 31. Through surface 31 there is formed a threaded aperture 32. The inner surface 33 (FIG. 5) of housing 30' curves inwardly to the working chamber as best seen at 133 in FIG. 4. The interior port housing 30 thus communicates directly with one endof the working chamber 36 (FIG. 5). Curved surface 33 provides a smooth transition of air entering the working chamber through aperture 32. Aperture 32 is threaded with a standard pipe thread to accommodate a male pipe connector coupling the outlet port to a utilization device for pressure applications or to exhausting means when the blower is coupled for suction application.

The front housing further includes a transfer duct 34 of the same configuration as outlet port 30 except the outer peripheral surface 35 is solid and does not permit the flow of air outwardly from the wall of the housing. As seen in FIG. 5, port 30 and duct 35 are spaced approximately 45 apart on the periphery of the housing and at opposite ends of the working chamber 36.

Surrounding a recessed central area 37 (FIG. 5) is a flat raised portion 38 (FIGS. 4 and 5) including a plurality of spaced circular recesses 39 aligned with shoulder 24 on the outer surface. Recesses 39 are not functionally employed in the front housing but are drilled through the rear housing at 139' (FIGS. 4 and 6) for mounting the motor to the rear housing.

Between the port 30 and transfer duct 35, the front and rear housings are narrowed at 40 as best seen in FIGS. 2 and 9. The inner surface of the narrowed portion of the housings, therefore, defines means for stripping the gas moving in the working chambers, forcing it out through the transfer duct 35 (or port depending on the interconnection of the housings) when the impeller is'rotating in a direction counterclockwise with respect to the front housing as seen in FIG. 5. For this purpose, the edges 42 and 43 of the stripper plate 41 thereformed extend into the widened working chamber closely adjacent the impeller as best seen in FIGS. l3, l6 and 17. In FIG. 4, the upper portion of the impeller is moving out of the plane of the drawing while the lower portion of the impeller is moving into the plane of the drawing. The inside walls of the narrowed portion 40 of the housings are thus spaced to define a blade pass portion 42 permitting the blades of the impeller to freely rotate through the narrowed area of the housings and working chambers.

Housings and 50 further include an annular recess 44 (FIGS. 5, 6 and 9) extending adjacent the outer edge of the working chamber 36 near flange 28 to re ceive a peripheral tongue or flange 69 on the impeller for sealing the working chambers of each of the housings from one another. Recess 44 is substantially rectangular with a flat surface extending radially outwardly from the hub 22 in a plane parallel to the plane to rotation of impeller 60.

The only significant differences between housings 20 and 50, as noted above, relate to the mounting of the motor to the rear housing as shown in FIG. 4. While the inner surface of hub 22 is only recessed, the corresponding hub 122 of the rear housing is drilled through at 121 (FIGS, 3, 4 and 6) permitting drive shaft 14 to extend therethrough and clear the housing. The face plate 13 of motor 12 is bolted to the annular shoulder 124 of the rear housing by means of a plurality of bolts (not shown) which extend through apertures 139' as seen in FIGS. 4 and 6. Thus, the rear housing is secured to the face plate of the motor. As noted above, the unit is mounted with the drive shaft oriented vertically. Thus, the shaft need not be supported by the blower housings. The clearance of hold 121 to shaft 14 is sufficiently small to avoid gas leakage around the shaft. In other mounting arrangements, if the shaft is horizontally oriented, it may be desired to support the shaft in the blower housings and include a sleeve bushing in aperture 121.

The outer surface of each of the housings includes a notch-shaped recess 45, 145 extending radially outwardly from the hub through shoulder 24, 124 and communicating with the recessed area 23, 123 to the space between a pair of fins 25 as seen in FIGS. 1, 3 and 11. Notch 145 on the rear housing permits free flow of air between the surface of the motor mount 13 and the abutting surface 124 of the rear housing such that pressure will not build up around the motor shaft bearing (not shown) tending to force lubrication therefrom. Notch 145 further permits air to be drawn through the normal air cooling channels of the motor for cooling purposes. Notch 45 in housing 20 is not functional.

The disc-shaped impeller 60 (FIGS. 4 and 7) includes a hub 62 having an aperture 64 extending therethrough and keyed for receiving motor shaft 14. A second aperture 63 is drilled and threaded at an angle through one side of hub 62 for receiving a set screw 63 which secures the impeller to shaft 14 as seen in FIG. 4. Surrounding each side of hub 62 is a recessed area 65 for reducing the weight of the impeller. A plurality of support ribs 66 extends radially at spaced intervals between hub 62 and the annular widened body 68 on opposite sides of the impeller as best seen in FIGS. 4 and 7 and as shown in detail in FIG. 8. Segment 68 of the impeller has flat outer surfaces parallel to and fitting between the flat surfaces 38 and 138 of the front and rear housings respectively. A clearance of approximately 000841.015 inch between the impeller and the housings permits free rotation of the impeller between the housings without permitting any significant movement in the central area of the impeller.

The outer periphery of the impeller is inwardly tapered to define a rectangular peripheral flange 69 extending beyond the working chamber into the tongue recesses 44 and 144 of the housings. A clearance of approximately 0.0100.0l5 inch permits free rotation of the impeller while flange 69 provides in cooperation impeller in the working area is a plurality of blades 70 extending outwardly on opposite sides of the narrowed portion 69 of the impeller as best seen in FIG. 4. Blades 70 terminate at outer edges 72 spaced approximately 0.010-0.012 ir'1ch from the peripheral walls 36 and 136' of the housings.

PARALLEL OPERATION As seen in FIG. 2, housings 20 and 50 are secured in the parallel mode of operation such that the inlet port of the rear housing is aligned with the transfer port 34 of the outer housing while the transfer port 134 of the rear housing is aligned with the outlet port 30 of the front housing. The parallel operation of the blower can best be understood by referring to FIGS. 12 and 13 which show the inlet and outlet port interconnections with the respective transfer ducts. In FIG. 12, air entering the blower in the direction indicated by arrow A travels through aperture 132 into the working chamber 136 of the rear housing. A portion of the entering air flows through the interconnected transfer duct 34 into the working chamber 36 of the front housing. The air is circulated through both working chambers in a spiral pattern by the impeller blades 70 (moving downwardly in the plane of the drawings in FIGS. 12 and 13). Thus, as the air travels along the annular path of the independent working chambers 36 and 136, it increases in pressure in a regenerative manner as is known in the art.

At the exit end of the working chambers, as seen in FIG. 13, the stripper plates 4.1 and 141 strip the air, now increased significantly in pressure, from the working chambers and the air exits from the blower as indicated by arrow A inthe figure. The air from working chamber 36 exits directly through the outlet 32 while air from working chamber 136 exits through the same aperture via the transfer duct 134 thereby combining the air flow of each of the working chambers to provide significantly increased flow volume (i.e., approximately double) over that achieved by a single chamber.

SERIES OPERATION To convert the blower for series operation, it is necessary only to remove securing bolts 11 and rotate the front and rear housings such that the transfer ducts 34 and 134 are in alignment, as seen in FIG. 14, and replace the bolts again securing the housings. In the series mode of operation illustrated in FIGS. 15l7, impeller blades 70 are moving into the plane of the drawing. Air enters inlet port 130, as indicated by arrow B in FIG. 15, and travels in a helical spiral path through working chamber 136. At theend of working chamber 136, as seen in FIG. 16, edge 142 of stripper plate 141 strips the air from the working chamber which is forced out through transfer duct 134 into aligned transfer duct 34 of front housing 20. The air is thus further pressurized passing through working chamber 36 also in a helical spiral. After completing its path through working chamber 36, the air is forced from working chamber 36 by edge 43 of stripper plate 41 and exits the'compressor through outlet port 30 as shown by arrow B inFIG. 17. In the series mode of operation, the output pressure is nearly double that achievable with a single chamber blower.

It is seen that by providing a relatively uncomplicated blower consisting of identical housings each including a transfer duct and port communicating with opposite ends of an annular channel defining a working chamher, a convertible series/parallel blower is provided which is relatively easily converted in the field for parallel operation where maximum flow is desired or series operation where maximum pressure is desired.

In the preferred embodiment, the housings were bolted together although it will become apparent to those skilled in the art that quick release securing means can be provided and may take the form of spring clamps or the like. To facilitate accurate alignment of the housings, indexing-pins can be provided which extend through the housing or other indexing means to facilitate rapid and accurate alignment of the housings in either the parallel positioning, as shown in FIG. 1, or series positioning as shown in FlG. 14. These and other modifications to the present invention, however, will become apparent to those skilled in the art and will fall within the scope and spirit of the invention as defined in the appended claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

l. A convertible series/parallel regenerative centrifugal blower comprising:

a first housing including an annular working chamber formed therein from one side of said housing and including air stripping means defining opposite ends of said working chamber spaced at a predetermined distance, said first housing including an outlet port communicating with one end of said working chamber and a transfer duct communicating with the other end of said working chamber;

a second housing including an annular working chamber formed therein from one side of said housing and including air stripping means defining opposite ends of said working chamber spaced at said predetermined distance, said second housing including an inlet port communicating with one end of said working chamber and a transfer duct communicating with the other end of said working chamber;

a substantially solid impeller rotatably mounted between said housings and including blades on opposite sides thereof extending into said working chambers for forcing air through said working chambers; and means for securing said first and second housings to each other in a. first relative position with said working chambers facing one another and with said outlet port of said first housing aligned with said transfer duct of said second housing and said inlet port of said second housing aligned with said transfer duct of said first housing such that said working chambers are coupled in parallel, and for securing said first and second housings to each other in a second relative position with said working chambers facing one another and with said respective transfer ducts aligned such that said working chambers are coupled in series. 2. The apparatus as deined in claim 1 wherein said first and second housings are made of substantially identical castings.

3. The apparatus as defined in claim 1 wherein said inlet and outlet ports each include a passageway extending through said housing.

4. The apparatus as defined in claim 1 wherein said first and second housings each include a recess extending inwardly from said one side of said housings at... around the outer periphery of said working chambers and wherein said impeller includes a peripheral tongue extending into said recesses and between said housings to define a seal between said working chambers.

5. The apparatus as defined in claim 4 wherein said inlet and outlet ports and said transfer ducts are positioned adjacent the outer periphery of the associated .working chambers of said housings.

6. The apparatus as defined in claim 5 wherein said outlet port and said inlet port are spaced an angular distance from the respective transfer duct of said first and second housings respectively of about 45.

7. The apparatus as defined in claim 1 wherein said impeller blades extend only partially into said working chambers.

8. A regenerative blower for a compressible fluid comprising:

a first housing including a curved channel formed therein from one side of said housing and terminated at opposite ends by an outlet port and a transfer duct respectively, said outlet port including a passageway extending through said housing;

a second housing including a curved channel formed therein from one side of said housing and terminated at opposite ends by an inlet port and a transfer duct respectively, said inlet port including a passageway extending through said housing;

impeller means rotatably mounted between said housings and including blades on opposite sides extending into said channels of said housings for forcing air through said channels in a spiral pattern; and

means for securing said first and second housings in a first relative position coupling said channels for parallel operation and in a second relative position wherein said first and second housings are rotated on an axis parallel to the axis of rotation of said impeller and with respect to each other to a second relative position for coupling said channels for series operation.

9. The blower as defined in claim 8 wherein said outlet port and transfer duct of said first housing are spaced at a predetermined distance from each other and wherein said inlet port and transfer duct of said second housing are spaced at said predetermined distance from each other.

10. The blower as defined in claim 9 wherein each of said curved channels extend in an annular path and are formed within its housing from one side thereof.

11. The blower as defined in claim 10 and further including means positioned between said outlet port and said transfer duct of said first housing and said inlet port and said transfer duct of said second housing for forcing air from said respective channels toward said outlet port or one of said transfer ducts.

12. The blower as defined in claim 11 wherein said forcing means includes a stripper plate extending between said outlet port and transfer duct of said first housing and said inlet port and transfer duct of said second housing.

13. A convertible series/parallel regenerative blower comprising:

a first generally disc-shaped housing including a channel formed in one side thereof and extending in an annular path between a port communicating with one end of said channel and through said first housing and a duct communicating with the other end of said channels, said housing including a recess formed in said one side and extending along the outer periphery of said channel and between said port and duct;

a second generally disc-shaped housing including a channel formed in one side thereof and extending in an annular path between a port communicating with one end of said channel and through said second housing and a duct communicating with the other end of said channel, said housing including a recess formed in said one side and extending along the outer periphery of said channel and between said port and duct, wherein said channels in said first and second housings have about the same radius of curvature and the respective ports and ducts are substantially equally spaced;

a generally disc-shaped impeller rotatably mounted to at least one of said housings and positioned between said housings, said impeller including blades on opposite sides which extend into said channels, said impeller further including a peripheral flange extending into said recesses of said housing to provide a seal between said channels; and means for securing said first and second housings in a first relative position with said channels facing each other and in which said port of said first housing and said duct of said second housing are aligned and said port of said second housing aligns with said duct of said first housing for parallel coupling of said channels, and for securing said first and second housings in a second relative position with said channels facing each other and in which said duct of said first housing is aligned with said duct of said second housing for series coupling of said channels. 14. The blower as defined in claim 13 wherein at least one of said housings includes an annular motor mounting boss for mounting a motor thereto and a central aperture for receiving a drive shaft of the motor to permit coupling the shaft to said impeller, said housing including a notch formed in the exterior side opposite said one side and extending radially outwardly through said boss.

15. The blower as defined in claim 13 wherein said channels are substantially rectangular in cross section.

16. The boss as defined in claim 13 wherein said impeller blades extend only partially into said channels.

17. The boss as defined in claim 13 wherein said ports are spaced from their associated ducts an angular distance of about 45. 

1. A convertible series/parallel regenerative centrifugal blower comprising: a first housing including an annular working chamber formed therein from one side of said housing and including air stripping means defining opposite ends of said working chamber spaced at a predetermined distance, said first housing including an outlet port communicating with one end of said working chamber and a transfer duct communicating with the other end of said working chamber; a second housing including an annular working chamber formed therein from one side of said housing and including air stripping means defining opposite ends of said workiNg chamber spaced at said predetermined distance, said second housing including an inlet port communicating with one end of said working chamber and a transfer duct communicating with the other end of said working chamber; a substantially solid impeller rotatably mounted between said housings and including blades on opposite sides thereof extending into said working chambers for forcing air through said working chambers; and means for securing said first and second housings to each other in a first relative position with said working chambers facing one another and with said outlet port of said first housing aligned with said transfer duct of said second housing and said inlet port of said second housing aligned with said transfer duct of said first housing such that said working chambers are coupled in parallel, and for securing said first and second housings to each other in a second relative position with said working chambers facing one another and with said respective transfer ducts aligned such that said working chambers are coupled in series.
 2. The apparatus as defined in claim 1 wherein said first and second housings are made of substantially identical castings.
 3. The apparatus as defined in claim 1 wherein said inlet and outlet ports each include a passageway extending through said housing.
 4. The apparatus as defined in claim 1 wherein said first and second housings each include a recess extending inwardly from said one side of said housings and around the outer periphery of said working chambers and wherein said impeller includes a peripheral tongue extending into said recesses and between said housings to define a seal between said working chambers.
 5. The apparatus as defined in claim 4 wherein said inlet and outlet ports and said transfer ducts are positioned adjacent the outer periphery of the associated working chambers of said housings.
 6. The apparatus as defined in claim 5 wherein said outlet port and said inlet port are spaced an angular distance from the respective transfer duct of said first and second housings respectively of about 45*.
 7. The apparatus as defined in claim 1 wherein said impeller blades extend only partially into said working chambers.
 8. A regenerative blower for a compressible fluid comprising: a first housing including a curved channel formed therein from one side of said housing and terminated at opposite ends by an outlet port and a transfer duct respectively, said outlet port including a passageway extending through said housing; a second housing including a curved channel formed therein from one side of said housing and terminated at opposite ends by an inlet port and a transfer duct respectively, said inlet port including a passageway extending through said housing; impeller means rotatably mounted between said housings and including blades on opposite sides extending into said channels of said housings for forcing air through said channels in a spiral pattern; and means for securing said first and second housings in a first relative position coupling said channels for parallel operation and in a second relative position wherein said first and second housings are rotated on an axis parallel to the axis of rotation of said impeller and with respect to each other to a second relative position for coupling said channels for series operation.
 9. The blower as defined in claim 8 wherein said outlet port and transfer duct of said first housing are spaced at a predetermined distance from each other and wherein said inlet port and transfer duct of said second housing are spaced at said predetermined distance from each other.
 10. The blower as defined in claim 9 wherein each of said curved channels extend in an annular path and are formed within its housing from one side thereof.
 11. The blower as defined in claim 10 and further including means positioned between said outlet port and said transfer duct of said first housing and said inlet port and said transfer dUct of said second housing for forcing air from said respective channels toward said outlet port or one of said transfer ducts.
 12. The blower as defined in claim 11 wherein said forcing means includes a stripper plate extending between said outlet port and transfer duct of said first housing and said inlet port and transfer duct of said second housing.
 13. A convertible series/parallel regenerative blower comprising: a first generally disc-shaped housing including a channel formed in one side thereof and extending in an annular path between a port communicating with one end of said channel and through said first housing and a duct communicating with the other end of said channels, said housing including a recess formed in said one side and extending along the outer periphery of said channel and between said port and duct; a second generally disc-shaped housing including a channel formed in one side thereof and extending in an annular path between a port communicating with one end of said channel and through said second housing and a duct communicating with the other end of said channel, said housing including a recess formed in said one side and extending along the outer periphery of said channel and between said port and duct, wherein said channels in said first and second housings have about the same radius of curvature and the respective ports and ducts are substantially equally spaced; a generally disc-shaped impeller rotatably mounted to at least one of said housings and positioned between said housings, said impeller including blades on opposite sides which extend into said channels, said impeller further including a peripheral flange extending into said recesses of said housing to provide a seal between said channels; and means for securing said first and second housings in a first relative position with said channels facing each other and in which said port of said first housing and said duct of said second housing are aligned and said port of said second housing aligns with said duct of said first housing for parallel coupling of said channels, and for securing said first and second housings in a second relative position with said channels facing each other and in which said duct of said first housing is aligned with said duct of said second housing for series coupling of said channels.
 14. The blower as defined in claim 13 wherein at least one of said housings includes an annular motor mounting boss for mounting a motor thereto and a central aperture for receiving a drive shaft of the motor to permit coupling the shaft to said impeller, said housing including a notch formed in the exterior side opposite said one side and extending radially outwardly through said boss.
 15. The blower as defined in claim 13 wherein said channels are substantially rectangular in cross section.
 16. The boss as defined in claim 13 wherein said impeller blades extend only partially into said channels.
 17. The boss as defined in claim 13 wherein said ports are spaced from their associated ducts an angular distance of about 45*. 